Ship hull for ice-breaking ship

ABSTRACT

A ship hull for ice-breaking ship of the kind where the opposite sides of the ship hull skin is given a particular curvature in order to increase the ability of the hull to break ice formations. The ship hull sides are given a wave-shaped curvature, such that the waves slope in direction backwards relative to the horizontal plane at an angle in the range from 0* to 25*. The ship sides are cantilevered outwards in a per se known fashion. In a preferred embodiment the steepest configuration of the wave surface has an angle in direction outwards relative to the vertical axis which is not less than 5*, preferably is not exceeding 20*.

United States Patent I Wilhelmsen SHIP HULL FOR ICE-BREAKING SHIP [451 Dec. 12,1972

FOREIGN PATENTS OR APPLICATIONS 54,173 6/1935 Norway ..114/40 Primary Examiner-Trygve M. Blix Attorney-Wenderoth, Lind & Ponack [5 7] ABSTRACT A ship hull for ice-breaking ship of the kind where the opposite sides of the ship hull skin is given a particular curvature inorder to increase the ability of the hull to break ice formations. The ship hull sides are given a wave-shaped curvature, such that the waves slope in direction backwards relative to the horizontal plane at an angle in the range from 0 to 25. The ship sides are cantilevered outwards in a per se known fashion. In a preferred embodiment the steepest configuration of the wave surface has an angle in direction outwards relative to the vertical axis which is not less than 5, preferably is not exceeding 20.

3 Claims, 2 Drawing Figures PATENTEI] DEC 12 m2 FIG] INVENTOR JENS WILHELMSEN FIG.2

ATTORNEYS The present invention relates to a new ship hull for ice-breaking ships, more particularly a ship hull con! figuration wherein the hull side is given a particular configuration with the aim to increase the ice-breaking ability of the ship hull side.

It is a well established principle in designing icebreaking ships to attempt to avoid plane vertical hull sides extending long greater parts of the ship, since the ice-breaking effect of plane vertical ship sides is small, simultaneously as the pressure force from the ice then will be directed straight against the ship sides and therefore may result in damages and in the worst case lead to that the ship hull is destroyed.

lce-breaking ships are therefore generally designed with outwardly cantilevered hull sides such that only a very short section of the mid portion of the ship, that is,

half-way between thebow and stem, extends more or less vertical.

In order to increase the ice-breaking effect of the hull is hitherto proposed to design the ship bow or bow section with a wave-shaped or saw-like curvature to increase the ice-breaking effect of the bow when the ship is moving forwardly against the ice edge, and hereby effecting that the ship is lifted up, such that the weight of the ship partlyrests against the ice edge and breaks it FIG. 1 is showing a schematic cross-section through the left half part of a ship hull configurated in accordance with the invention, while FIG. 2 is showing a schematic lateral view of the ship hull illustrated in FIG. 1.

In FIG. 1 the reference number 2 designates the'bottom of the ship hull, 4 designates the main deck, 7

, designates a partition wall, while 6 designates the wavedown. A such design of the ship bow has however, of

several reasons, not proved to be particularly good, and is, as far is known, abandoned.

The present invention. relates to a new embodiment of a ship hull for ice-breaking ships,of the kind where the hull side is given a curvature in order to increase the ability of the hull to break the ice, and the present invention is generally characterized therein that the ship hull sides are given a wave shaped curvature with the waves sloping backwards relative to the horizontal at a desired angle having from 0 to 25 simultaneously as the ship hull sides are cantilevered outwardly in per se known way.

The new ship hull configuration involves in several ways an improvement in connection with ice-breaking ships. An important advantage is thus that the particular wave shape implies that the flank angle of the ship sides against the adjacent ice masses varies at all levels and thereby creates a pulsating effect which implies anincrease in the ice breaking ability of the hull, not only at the forward section of the ship, but also along the ship sides, a fact which is of large importance in connection with long ships. The new ship hull configuration must thus be assumed to be particularly suitable for large ships, with large mass forces and large engine effect, since these forces can in an effective way be utilized with the aim to break the ice masses passing along the sides of the ship.

In a preferred embodiment a ship hull in accordance with the invention is configurated such that the wave has a surface such that a tangent through a vertical plane through the steepest area of the wave surface is directed outwards relative to the vertical axis and presenting an angle of not less than 5, but not larger than 20. The center line through the wave-shaped ship hull side measured in a vertical plane should be straight lined and slope outwards at an angle B of about 70 from the horizontal plane.

The invention shall be described in the following with reference to the accompanying drawing, wherein:

shaped ship side. The length of the waves are not particularly critical, and may for instance be given a length of l 2 m. The letters LWL designate the draught of the ship when loaded, MWL is the mean draught line, while BWL is the water line under light draught. The line 8 is the mean line or center line through the waveshaped ship hull side measured in a vertical plane, such that the angle [3 designates the angle between the mean line and the horizontal plane, as shown. The steepest course of the wave surface will as shown be located in the areas designated with the letter S on each wave curvature, and as previously mentioned the angle 8 with the horizontalplane must not be less than 5. The tangent drawn in a vertical plane at the steepest area of the wave surface is designated with the letter T.

FIG. 2 illustrates how the wave curvature illustrated in FIG. 1 is localized on the ship hull side. Thewave curvature, which is indicated with the lines 10,10, etc., are preferably substantially straight, and are sloping downwards in direction backwards along the ship hull and presenting an angle a with the horizontal plane and which as previously mentioned should be selected in the range from 0 to 25, in dependence of several factors, such as the size of the ship, the engine force, the length of the ship, etc. The wave curvature area is preferably limited to that section of the hull laying between the points A and B, which designate the substantially straight-lined portion of the ship hull viewed in an horizontal projection.

The ship sides are preferably constructed of pressed steel plates having corrugations or waves as shown, since such waves will present a large resistance against deformation due to the pressure from the ice masses and the ship propulsion machinery. Calculations have shown that the production costs and the material weights will be lower when utilizing the ship hull construction in accordance with the invention than utilizing corresponding conventional ship hull sides and with the same constructional strengths. The invention is particularly developed with the aim to be used in connection with large tankers for use in arctic areas.

What is claimed is:

1. Ship hull for an ice-breaking ship whereby the ship hull skin is given a particular curvature to increase the ability of the hull to break ice formations comprising a hull having ship hull sides with a wave-shaped curvature, the waves of said curvature sloping in a direction backwards relative to the horizontal plane at an angle in the range from 0 to 25 and 'said ship sides being cantilevered outwardly.

2. Ship hull in accordance with claim 1 wherein the steepest configuration of said wave-shaped curvature has an angle in a direction outwardly relative to a vertical axis which is not less than 5 and not exceeding 20.

3. Ship hull in accordance with claim 1 wherein center line through said wave-shaped curvature measured in a vertical plane is rectilinear and is cantilever'ed outwardly at an angle of about 

1. Ship hull for an ice-breaking ship whereby the ship hull skin is given a particular curvature to increase the ability of the hull to break ice formations comprising a hull having ship hull sides with a wave-shaped curvature, the waves of said curvature sloping in a direction backwards relative to the horizontal plane at an angle in the range from 0* to 25* and said ship sides being cantilevered outwardly.
 2. Ship hull in accordance with claim 1 wherein the steepest configuration of said wave-shaped curvature has an angle in a direction outwardly relative to a vertical axis which is not less than 5* and not exceeding 20* .
 3. Ship hull in accordance with claim 1 wherein center line through said wave-shaped curvature measured in a vertical plane is rectilinear and is cantilevered outWardly at an angle of about 70*. 